Ethylene and dienes, and optionally other olefins, can be copolymerized by using a polymerization catalyst which is a selected iron complex of a 2,6-pyridinecarboxaldehyde-bis(imine) or a 2,6-diacylpyridinebis(imine). The resulting copolymers contain branches with olefin groups, and in some instances cyclic structures resulting from cyclization of certain of the dienes.
Ethylene and its copolymers are important items of commerce. The copolymerization of ethylene with alpha, omegadienes in many instances, such as with Ziegler-Natta and metallocene type catalysts, yields crosslinked polymers since both of the olefinic bonds in the diene may be polymerized by these catalysts. Indeed to make polyolefins (including polyethylenes) having branches containing olefinic bonds, nonconjugated external-internal diolefins such as 1,4-hexadiene (or other types of dienes having two olefinic groups of differing reactivities) must be used.
It has now been found that selected iron or cobalt complexes of a 2,6-pyridinecarboxaldehydebis(imines) or 2,6-diacylpyridinebis(imines) may be used to copolymerize ethylene and various dienes, and that the resulting copolymers contain branches having terminal olefin groups. In some instances part of the diene which is incorporated into the copolymer is present as a saturated cyclic structure which is part of the polymer main chain. U.S. Pat. No. 5,955,555, WO99/12981, WO99/46302, WO99/46303, WO99/46304, WO99/46308, WO99/50318 (corresponding to U.S. patent application Ser. No. 09/273,409, filed Mar. 22, 1999), WO99/62963 (corresponding to U.S. patent application Ser. No. 09/317,104, filed May 21, 1999), WO99/62967 (corresponding to U.S. patent application Ser. No. 09/317,563, filed May 21, 1999), WO00/15646, WO00/24788, WO00/32641 and WO00/50470 (all of which are incorporated by reference herein for all purposes as if fully set forth) describe the use of selected iron or cobalt complexes of a 2,6-pyridinecarboxaldehydebis(imine) or a 2,6-diacylpyridinebis(imine) as polymerization catalysts for ethylene and other olefins. No mention is made of the use of dienes as comonomers.
This invention concerns a process for preparing an olefin copolymer, comprising the step of contacting:
(a) a monomer component comprising ethylene and a diene of the formula H2Cxe2x95x90CH(CH2)nCHxe2x95x90CHR19, wherein R19 is hydrogen or an n-alkyl containing 1 to 18 carbon atoms, and n is 0 or an integer of 1 to 28; and
(b) an active copolymerization catalyst, under conditions to copolymerize the monomers of the monomer component, wherein the active copolymerization catalyst comprises an iron complex of a tridentate ligand of the formula (I) 
wherein:
R1, R2, R3, R4 and R5 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group, provided that any two of R1, R2 and R3 vicinal to one another, taken together may form a ring; and
R6 and R7 are each independently aryl or substituted aryl.
Optionally, the monomer mixture may further comprise, in addition to ethylene and the diene, one or more xcex1-olefins of the formula H2Cxe2x95x90CHR20, wherein R20 is n-alkyl containing 1 to 18 carbon atoms.
This invention also concerns an olefin copolymer comprising the repeat units:
(a) xe2x80x94CH2CH2xe2x80x94 (II); 
wherein m is 1, 2, 3 or 4; and
(c) (1) when m is 2, 3 or 4, one or more of 
(2) when m is 1, one or more of (V) and (XIII);
wherein:
p is equal to m; and
r is equal to one or more of mxe2x88x921, m, and m+1.
This copolymer may be derived when the monomer component comprises ethylene and one or more dienes of the above formula wherein n is 1, 2, 3 or 4. In the event that the monomer mixture optionally contains one or more dienes wherein n is 0 (butadiene) or an integer of from 5 to 28, or one or more xcex1-olefins of the above formula, the copolymer will further comprise the respective repeat units (XII) and (XIII) 
wherein ml is 0 or an integer of from 5 to 28 (e.g., equal to n from the corresponding diene monomer), and R20 is as defined above (equal to R20 from the corresponding xcex1-olefin monomer).
The copolymers resulting from the process in general contain at least some residual olefinic unsaturation derived from the diene monomer (see repeat units (III) and (XII)), but are preferably in and of themselves substantially non-crosslinked. Thus, the invention still further concerns a substantially non-crosslinked copolymer of ethylene and a diene of the formula H2Cxe2x95x90CH(CH2)nCHxe2x95x90CHR19, wherein R19 is hydrogen or an n-alkyl containing 1 to 18 carbon atoms, and n is 0 or an integer of 1 to 28, containing residual unsaturation derived from the diene monomer. Preferably this copolymer contains one or more of the repeat units 
wherein p is 2, 3 or 4; and r is 0, 1, 2, 3, 4, or 5.
The resulting copolymers are crosslinkable at least in part due to the presence of the residual olefinic unsaturation. This residual olefinic unsaturation may also be reacted with a variety of functional compounds to impart various types of functionality to the copolymer.